Evidence of Antineutrinos from Distant Reactors Using Pure Water at SNO

Area of Science:

• Particle Physics
• Astrophysics
• Nuclear Physics

Background:

• Cherenkov detectors are typically used for neutrino detection.
• Detecting reactor antineutrinos from distant sources presents significant challenges due to low event rates and background noise.
• Previous analyses in large water Cherenkov detectors have focused on higher energy events.

Purpose of the Study:

• To report the first evidence of reactor antineutrinos detected in a Cherenkov detector.
• To analyze low-energy events from distant nuclear reactors.
• To establish a new method for antineutrino detection and characterization.

Main Methods:

• Utilized data from the SNO+ Cherenkov detector.
• Analyzed events with energies lower than in previous large water Cherenkov detector analyses.
• Employed two distinct analytical methods to differentiate reactor antineutrinos from background noise.
• Collected 190 days of data for the analysis.

Main Results:

• Reported the first evidence of reactor antineutrinos in a Cherenkov detector.
• Detected antineutrinos originating from nuclear reactors located 240 km away.
• Achieved a combined statistical significance of 3.5σ for the observed antineutrino signal.
• Demonstrated consistent results between the two analytical methods used.

Conclusions:

• The SNO+ experiment has successfully detected reactor antineutrinos in a Cherenkov detector.
• This finding opens new avenues for studying neutrinos and their interactions.
• The analysis demonstrates the capability of Cherenkov detectors to observe low-energy antineutrinos from distant sources.